An important element is that political marriages at the time were affairs of state, and often entered into for diplomatic purposes. This was certainly true in Henry's first marriage to Catherine of Aragon, who was the widow of his older brother Arthur. Catherine was the daughter of Ferdinand and Isabella of Spain, and the original marriage had been arranged by Henry's father, Henry VII to secure a dynastic relationship with Spain. On Arthur's death, the elder Henry arranged the second marriage solely to maintain the relationship.
Even more important was Henry's need for a male heir. The Tudor dynasty's claim to the throne was tenuous at best; Henry VII claimed it by conquest after he defeated Richard III at the Battle of Bosworth Field. Henry divorced his first wife and had the second (Anne Boleyn) executed because they were unable to produce a male heir. He only secured that heir by his third wife, Jane Seymour, who died in childbirth. Since the son, the future Edward VI was sickly as a child, Henry married twice more in hopes of producing an heir. He himself was getting up in age, but married much younger women. Neither marriage was successful, He annulled his marriage to Anne of Cleves because she was unattractive to him (he called her the Flanders Mare) and the feeling was mutual. His fifth wife, Catherine Howard was guilty of adultery and beheaded. His final wife, Catherine Parr, who survived him was basically a nursemaid to him and surrogate mother to his children.
The point is further illustrated by the marriage of his daughter, Mary I to Philip II of Spain, again a dynastic marriage solely for political purposes. After Mary's death, Philip proposed marriage to her half sister, Elizabeth I, who coyly avoided the subject. Philip's fury at being rejected by Elizabeth (once he took the hint) was one of several reasons which led to the launch of the Spanish Armada to attack Spain.
The importance of dynastic marriages was perhaps best illustrated not by England but by a famous statement from Austria:
Others may make war, but thou happy Austria, marry.